2018 Apple Maturity Assessment: Mid-October Report

GoldRush apples in a tall-spindle planting. Photo: Kathy Hunt, University of Maryland

Not only has the fall foliage color been delayed this year, but red color development in apple fruit has lagged as well. The onset of cooler weather and frosts during the third week in October finally began to improve red color development in late-season apples. While Fuji fruit were tree-ripe in mid-October, they still only had about 40 percent red coloration.

This month we added four October varieties to our evaluations: Fuji, GoldRush, Granny Smith and Cripps Pink (Pink Lady). Data for all four varieties are shown in Table 1.

Fuji and GoldRush

By October 19, Fuji fruit at Keedysville had softened considerably and had excellent eating quality. They were developing varietal flavor and texture with little starch left in the fruit. Despite their large size and good quality, the fruit sampled on October 19 had not developed water core. This lack of water core was likely due to the warmer weather, which delays its onset.

While only a few yellow fruit were seen on October 7, most of the fruit on the trees had developed the required size and color by October 19. GoldRush were the largest fruit we evaluated, with high soluble solids (17.6 Brix). Despite that very high level of sugar, GoldRush still tasted acidic. When we measured the starch pattern index of these greenish-yellow fruit, we noticed great variability. The mean starch pattern index was 4.8 with individual fruit ranging from 2 to 8, using the Cornell Starch Chart.

The high level of sugar in the fruit and rough peel makes GoldRush susceptible to fruit cracking. While we did not see any fruit cracking in our trials in Central Maryland, some cracking was seen at the University of Maryland farm on Maryland’s Eastern Shore (Photo 2). Apples at that location typically mature 7 to 10 days ahead of our trial location in Washington County, Maryland. Based on the damage seen on the Eastern Shore, GoldRush cracking is likely to begin soon in mid-Atlantic orchards.

Granny Smith and Cripps Pink

With the warmer weather, red color was slow to develop in these late-October varieties. As expected, Granny Smith was maturing ahead of Cripps Pink and ready for long-term storage in the third week of October. Based on the firmness and starch readings, Cripps Pink should be ready to pick by Election Day in November. Based on our October 19 data (Table 1), both varieties appear to be maturing on schedule.

These observations were made by spot-picking fruit grown on supported trees budded on to size-controlling rootstocks. Small differences in microclimate or orchard management practices can make a large difference in maturation. Management practices that might hasten fruit maturity are summer PGR applications to enhance return bloom, mechanical pruning to increase red color development, choice of rootstock and the use of stop-drop sprays.

Table 1. Changes in maturity and quality of late-season apple cultivars picked in Central Maryland in October 2018.

October Apples – Central Maryland (Keedysville, Washington County)

Cultivar

Date

Diameter (inches)

Red Color (%)

Ground Color

Firmness (pounds)

Starch Pattern (1 – 8)

Soluble Solids (°Brix)

Fuji (BC-2)

October 7, 2018

3.1

28.0

Greenish yellow

14.5

6.4

15.3

October 19, 2018

3.2

42.0

Greenish yellow

14.4

7.7

14.4

GoldRush

October 7, 2018

3.2

0.0

Yellowish green

21.9

2.7

15.1

October 19, 2018

3.3

12.0

Greenish yellow

21.3

4.8

17.6

Granny Smith

October 7, 2018

3.1

0.0

Whitish green

19.8

3.8

12.0

October 19, 2018

3.2

12.0

Whitish green

17.6

4.9

14.0

Cripps Pink

October 7, 2018

2.9

18.0

Greenish yellow

21.5

1.7

12.3

October 19, 2018

3.1

45.0

Greenish yellow

19.5

4.9

13.6

Photo 1. Color development in GoldRush apples in a tall-spindle planting at the Western Maryland Research and Education Center in Keedysville. Photo: Kathy Hunt, University of Maryland

Photo 2. Rain cracking of GoldRush apples picked on Maryland’s Eastern Shore in mid-October. Cracking was seen on heavily-cropped trees at this location following recent heavy rains. Photo: Mike Newell, University of Maryland

Photo 3. Red color development in tree-ripe Fuji apples at Keedysville MD on October 19, 2018. While the percentage of red color was increasing, the depth of color was still reduced by warm weather. Photo: Kathy Hunt, University of Maryland